The present invention relates to a brake booster for automotive vehicles comprising a low-pressure casing including two casing parts which are sealingly connected to each other at the casing periphery, the low-pressure casing being sealingly subdivided into a low-pressure chamber and a working chamber by an axially movable wall, the working chamber being connectible to the low-pressure chamber or to atmosphere by a mechanically actuatable control valve, and a force-transmitting member axially penetrating the movable wall in a sealed relationship thereto.
A generally desired weight reduction of the automotive vehicles makes it necessary to design all component parts and assemblies of the automotive vehicle in a maximum possible weight-saving way. As to the brake booster, a weight reduction can be accomplished by having the transmittance of force from the master cylinder of the brake unit to that component of the automotive vehicle to which the brake booster is secured-conventionally the splashboard-no longer effected via the low-pressure casing but rather via a force-transmitting member axially penetrating the low-pressure casing, for example, tie rods, such as disclosed in German Patent DE-OS No. 2,845,794, or a central reinforcement tube such as disclosed in a copending U.S. application of J. Belart and F. Weinecke, Ser. No. 061,113, filed July 26, 1979 and assigned to the same assignee as the present application. In these arrangements, the casing parts which form the low-pressure casing only have to absorb those forces that are caused by the occurring differences in pressure. By constructing the low-pressure casing of lighter weight material, a weight reduction of the booster itself was achieved. However, it is not possible to further reduce its weight by reducing the size of the low-pressure casing, since the necessary effective surface of the movable wall in the low-pressure casing is determined by the magnitude of the partial vacuum available and by the brake boosting force required.